License vital.vim under CC0 or WTFPL

Currently, vital.vim is released under NYSL.
NYSL is a bit restrictive counterpart of Unlicense in Japan and a tool to insist "my software, public domain".

This license is good for a trivial, private software developed in Japan because the license document was originally written in Japanese and not messed up by a lawyer.

However, NYSL have some problems when a open-source software is released under it.

1. The NYSL code cannot be used in GPL products, since FSF stated nothing about NYSL.
2. Nobody knows NYSL is effective as PD outside of Japan as Unlicense.
3. NYSL is not verified as a open source license.
4. NYSL has no official documents written in English.
5. NYSL is no written by a lawyer.

CC0 can resolve all the problems except the third.

List of licenses

• CC0 waives rights or permits anything if rights cannot be waived.
• WTFPL permits anything but waives nothing.
• Unlicense permits anything and waives rights.
• NYSL allow anything and waives some rights, but the other rights are reserved.
• No declarations mean all rights are reserved to the author.

The issue names no specific file or test; start by locating the repository's current NYSL license declaration and reviewing the unresolved choice between CC0 and WTFPL. Done means replacing the NYSL licensing information with the agreed license and keeping the repository's licensing statements consistent.